Well, the "shortest file name" is indeed not possible, because TC doesn't have options to compare the members from within a group with custom options,
but in the field "select by name/extension" you can select files from a certain drive with a regular expression:
e.g.
to select all files from drive d:
For the name length compare it won't be easy to find a solution, even with an external program, as you need to preserve the group order.
If you have only two files per group then you could export the results as a list of file names (mark all files and use TC's
cm_CopyFullNamesToClip command), copy it to a text file and use some script on it that removes the shorter name from it, copy the modified file content to clipboard and use the TC command
cm_LoadSelectionFromClip.